Effects of different cultivated or weed grasses, grown as pure stands or in combination with wheat, on take‐all and its suppression in subsequent wheat crops

Abstract

Grass species were grown in plots, as pure stands or mixed with wheat, after a sequence of wheat crops in which takeall ( Gaeumannomyces graminis var. tritici ) had developed. Annual brome grasses maintained take-all inoculum in the soil as well as wheat (grown as a continuous sequence), and much better than cultivated species with a perennial habit. Take-all developed more in wheat grown after Anisantha sterilis (barren brome) or Bromus secalinus (rye brome), with or without wheat, than in continuous grass-free wheat in the same year, where take-all decline was apparently occurring. It was equally or more severe, however, in wheat grown after Lolium perenne (rye-grass) or Festuca arundinacea (tall fescue), despite these species having left the least inoculum in the soil. It was most severe in plots where these two grasses had been grown as mixtures with wheat. It is postulated that the presence of these grasses inhibited the development of take-all-suppressive microbiota that had developed in the grass-free wheat crops. The effects of the grasses appeared to be temporary, as amounts of take-all in a second subsequent winter wheat test crop were similar after all treatments. These results have important implications for take-all risk in wheat and, perhaps, other cereal crops grown after grass weed-infested cereals or after set-aside or similar 1-year covers containing weeds or sown grasses, especially in combination with cereal volunteers. They also indicate that grasses might be used experimentally in wheat crop sequences for investigating the mechanisms of suppression of, and conduciveness to, take-all.

Evidence that wheat cultivars differ in their ability to build up inoculum of the take‐all fungus, Gaeumannomyces graminis var. tritici, under a first wheat crop

“…The amount of inoculum in the soil at the time of sowing a susceptible crop greatly influences the amount of primary infection that occurs in that crop and so helps to determine final disease severity (Bailey & Gilligan, 1999). Much of the previous research on take‐all inoculum has focused on the capability of other crops and grass weeds to maintain and carry over inoculum in a break year (Gutteridge et al. , 2006), the survival of Ggt inoculum in the field post‐harvest (Macnish & Dodman, 1973; Bithell et al.…”

The role of models for multicriteria evaluation and multiobjective design of cropping systems for managing weeds

“…Among the existing weed‐dependent organisms, we should focus on species that are strongly impacted by cropping systems (since we want to evaluate them) and that affect crop production and/or biodiversity. The first guild that springs to mind are soilborne crop pathogens because they rarely disperse from field to field (Prew, ) and are thus most affected by field history; in addition, they can infect weeds which thus transmit crop diseases in time and in space (Gutteridge et al ., ).…”

“…We illustrated the integration of biotic interactions with the soilborne crop pathogen Gaumannomyces graminis vs. tritici causing take‐all disease in straw cereals and important yield losses (up to 50%, Schoeny et al ., ). This fungus mostly depends on the cropping system (Ennaïfar et al ., ) and can infect several grass weeds (Gutteridge et al ., ). Simple models already existed in the literature predicting (i) disease incidence from past crops, crop management variables and weather variables (Ennaïfar et al ., ) and (ii) the resultant crop yield loss from disease incidence and nitrogen fertiliser (Schoeny et al ., ).…”

“…They can also host other pests such as crop pathogens (e.g. take‐all disease of cereals, Gutteridge et al ., ). Consequently, farmers largely rely on herbicides to control weeds, which are the main obstacle for switching to Integrated Pest Management (INRA, ).…”

Cultural Practices Influencing Biological Management of Crop Diseases

“…Take-all developed more in wheat grown after Anisantha sterilis (barren brome) or Bromus secalinus (rye brome) with or without wheat, than in continuous grass-free wheat in the same year, whereas take-all decline was apparently occurring. While annual grass species were found to be more effective hosts of the take-all pathogen, some of the perennial grasses were more effective obstacle to the development of suppression (Gutteridge et al 2006 ) .…”